I vaguely recall a sci-fi novel a decade or so ago that featured a wasp-waisted hypersonic bullet. Which according to the author would theoretically accelerate as it traveled due to a quirk in the aerodynamics - riding the sonic shock wave or something like that.

Checking out TNE's Fire, Fusion and Steel which has a extensive system for creating gauss and mass driver weapons. [snip] Gauss weapons can have gyroscopic compensators or inertial compensators at higher TLs. The IC is a harness worn by the user and the weapon is attached.

Well, this then could solve the question I originally posed - the Zero G trait for Gauss weapons. In fact, this conceivably could be applied to all slug throwers. I'm guessing this is TL 12+?...

As I see more comments accumulate, perhaps the variable power idea negates the Gauss weapons' inherent advantage of high hitting/penetration power. But the IC harness sounds as though it could be worth it for fighting off heavily armored boarding parties, especially with high tech, high power ammo. It could add the Bulky trait, add weight and cost and require power (rechargeable batteries?) as the trade off...

Most of the things that I could add here have been covered. One point to emphasize about recoil is the muzzle energy is mass times velocity squared, while momentum is mass times velocity, so the 4 gram 1500 meter per second Gauss round has a lower momentum than a heavy normal velocity round of equal muzzle energy.

One point that hasn't come up is that a conventional round propels not just the bullet out the barrel, but also a lot of the propellant gases. Those gases aren't pushing on the weapon to generate recoil once they clear the barrel, but they do until then. With an energetic propellant, the mass of the bullet is quite a bit larger than the propellant gases, but there's more coming out the barrel of a conventional rifle than the bullet.

Another point not mentioned is the Advanced Combat Rifle, described as the ultimate development of rifles with chemical propellant. It has all the firing solution and helmet mounting stuff included, well before the Gauss rifle becomes available. Presumably all that would be present in the first military Gauss rifle, because it's standard equipment by then.

There's also the matter of stabilizing a round. Fitting four grams of anything into a 4 mm diameter round gives a long stick of matter. Spin stabilization requires higher spin rates for longer rounds -- really high for a Gauss round for any real world metal. But maybe at TL12, the armor piercing core could be some science fiction 40 density metal, and the jacket is normal 8 density mild steel. But even that isn't a complete solution, because putting the high density stuff in the core doesn't help the spin stabilization as much as a dense outer ring would. Maybe the puzzle of how to put so much spin on the round is part of the reason the Gauss rifle is a TL12 development.

Variable power gauss weapons? I like that, might have to investigate it for a future adventure or supplement

To be honest, I thought I saw that already, described as an optional version that could fire the rounds at selectable velocity, even as slow as subsonic, which makes a practically silent weapon. Real weapons with "silencers", more formally "suppressors", are still pretty darn loud, not at all like they're portrayed in most movies. But a subsonic Gauss round might be as quiet as a movie silencer.

To save looking things up, the speed of sound is about 340 meters per second. To offer a 10% safety margin, assume that the subsonic Gauss round is about 306 meters per second. That's 20.4% the regular velocity, so it has about 4% of the regular velocity round's muzzle energy -- very close to that of a .22 LR round. So by switching the Gauss rifle from full power to subsonic, you go from the ultimate development of the slug throwing weapon to the rifle I fired as a kid at summer camp. At range, a sturdy leather jacket could probably stop it.

Of course, if the weapon can be tuned down to subsonic, it can also be tuned to an in-between velocity with enough power to do its damage while reducing the recoil enough for the soldier's ability to handle the recoil. Maybe the tunable Gauss rifle has five settings, for full, 80%, 60%, 40%, and subsonic, with full, 64% 36% 16%, and 4% damage.

Most of the things that I could add here have been covered. One point to emphasize about recoil is the muzzle energy is mass times velocity squared, while momentum is mass times velocity, so the 4 gram 1500 meter per second Gauss round has a lower momentum than a heavy normal velocity round of equal muzzle energy.

One point that hasn't come up is that a conventional round propels not just the bullet out the barrel, but also a lot of the propellant gases. Those gases aren't pushing on the weapon to generate recoil once they clear the barrel, but they do until then. With an energetic propellant, the mass of the bullet is quite a bit larger than the propellant gases, but there's more coming out the barrel of a conventional rifle than the bullet.

Another point not mentioned is the Advanced Combat Rifle, described as the ultimate development of rifles with chemical propellant. It has all the firing solution and helmet mounting stuff included, well before the Gauss rifle becomes available. Presumably all that would be present in the first military Gauss rifle, because it's standard equipment by then.

There's also the matter of stabilizing a round. Fitting four grams of anything into a 4 mm diameter round gives a long stick of matter. Spin stabilization requires higher spin rates for longer rounds -- really high for a Gauss round for any real world metal. But maybe at TL12, the armor piercing core could be some science fiction 40 density metal, and the jacket is normal 8 density mild steel. But even that isn't a complete solution, because putting the high density stuff in the core doesn't help the spin stabilization as much as a dense outer ring would. Maybe the puzzle of how to put so much spin on the round is part of the reason the Gauss rifle is a TL12 development.

Variable power gauss weapons? I like that, might have to investigate it for a future adventure or supplement

To be honest, I thought I saw that already, described as an optional version that could fire the rounds at selectable velocity, even as slow as subsonic, which makes a practically silent weapon. Real weapons with "silencers", more formally "suppressors", are still pretty darn loud, not at all like they're portrayed in most movies. But a subsonic Gauss round might be as quiet as a movie silencer.

To save looking things up, the speed of sound is about 340 meters per second. To offer a 10% safety margin, assume that the subsonic Gauss round is about 306 meters per second. That's 20.4% the regular velocity, so it has about 4% of the regular velocity round's muzzle energy -- very close to that of a .22 LR round. So by switching the Gauss rifle from full power to subsonic, you go from the ultimate development of the slug throwing weapon to the rifle I fired as a kid at summer camp. At range, a sturdy leather jacket could probably stop it.

Of course, if the weapon can be tuned down to subsonic, it can also be tuned to an in-between velocity with enough power to do its damage while reducing the recoil enough for the soldier's ability to handle the recoil. Maybe the tunable Gauss rifle has five settings, for full, 80%, 60%, 40%, and subsonic, with full, 64% 36% 16%, and 4% damage.

You're right on regarding the propellant contributing to recoil. Gauss weapons would have less recoil for a given round mass/muzzle velocity simply by not having propellant.

As I indicated earlier, reducing the muzzle velocity with a standard Gauss weapon would quickly reduce the effectiveness, given the light weight of the round. the armor piercing trait would go away pretty quickly, and the damage would drop dramatically as muzzle velocity goes down. cloth armor would very quickly be all that was required to stop a reduced MV Gauss round, much like small calibre, sub-sonic rounds currently don't have much penetration power. There also isn't anything to say that you can't increase the power per shot, reduce the rate of fire, and step up your penetration and damage. For game balance, there would have to be a steep tradeoff in energy use, maybe 1/5 the shots from a magazine, since you're having to ramp up the power without providing more coils, as you do with the Gauss Sniper Rifle.

I had a player who wanted to use all sorts of specialty ammo with a standard Gauss pistol. I had to explain that APDS rounds just won't work with a Gauss pistol, since a sabot wouldn't be beneficial for a Gauss Weapon. It's just a different mechanism. What I did allow was very expensive Gauss Hi-Pen ammo that used a bonded superdense penetrator, so there is your ultra-high density core material. Damage was reduced, but penetration increased considerably, even in a Gauss pistol. Its just a matter of having sufficient mass, and reducing the impact footprint. I already imagine the rounds as being finned, wasp-waisted, pointed teardrop flechettes, with a hollow point. I imagine it does most of its damage through hydrostatic effects. If you wanted to be really ugly and use a DU core, you could get some nasty high-temp blow through on hard targets.

Ye default shotgun fires off an eighteen millimetre shell; this might be a tad too large to stuff into a standard gauss rifle.

In an atmosphere, the gauss bullet does have to be aerodynamic, and have enough penetrative power to punch through personal armour, and deliver substantial energy to the target without passing through the body, completely.

As I understand physics, optimal subsonic speed is eighty five percent of mach, after which, it tends to get unstable.

steve98052 wrote: ↑
There's also the matter of stabilizing a round. Fitting four grams of anything into a 4 mm diameter round gives a long stick of matter.

Wolfram and DU has a density of ~19 g/cm³, so 4 g would be 4/19 ≈ 0.21 cm³ = 210 mm³.

A 4 mm diameter projectile has a cross-section of π2² ≈ 12.5 mm². At 210 mm³ it would be 210 / 12.5 ≈ 17 mm long, not at all unreasonable.

Depleted Uranium isn't ferromagnetic, so you couldn't launch a round "made" of DU with a Gauss weapon, but you could use DU as the core with a soft outer casing. Depleted Uranium is pyrophoric, flammable, self-sharpening, and highly toxic. A problem with using DU rounds, is that the dust created by DU fragmenting and burning, creates a radioactive toxin that lingers in the environment for a while. I'm guessing that most local governments, even if low law level, would be pretty frowny on people using DU rounds, as likely would the Imperium.

T4 Fire,Fusion and Steel, indicates that Bonded Superdense is ~15 g/cm³, so less than DU, but likely ferromagnetic, since there don't seem to be any special requirements for boot magnets to hold onto Superdense hulls. Also, If your round is pointed, has a teardrop tail, finned, and wasp-waisted, even though it is 4 mm, that won't be its diameter for its entire length, so you could easily justify a 4 g 4 x 40mm round, using a Superdense core, wrapped with a layer of highly magnetically reactive polymer/metallic sandwich, for reduced power use.

. . . There also isn't anything to say that you can't increase the power per shot, reduce the rate of fire, and step up your penetration and damage. For game balance, there would have to be a steep tradeoff in energy use, maybe 1/5 the shots from a magazine, since you're having to ramp up the power without providing more coils, as you do with the Gauss Sniper Rifle.
. . .

I would argue that if TL12 allowed for a power boost, it would have been built that way. Maybe there's only so much magnetic energy that can be dumped into the barrel of a Gauss weapon without disrupting the high temperature superconductor (a known limitation of existing superconductors that might also exist in TL12 superconductors). Maybe too much acceleration will tear the projectile to pieces, or cause so much inductive heating that it melts -- or vaporizes. I'd rule that it's as good as it can be, and to get more power requires a longer barrel.

Wolfram and DU has a density of ~19 g/cm³, so 4 g would be 4/19 ≈ 0.21 cm³ = 210 mm³.

A 4 mm diameter projectile has a cross-section of π2² ≈ 12.5 mm². At 210 mm³ it would be 210 / 12.5 ≈ 17 mm long, not at all unreasonable.

Correction accepted. I did the math right, but I did it a while ago, and I was calculating the results of different questions. I mixed up the results of one calculation with another.

But this reminds me of another unaddressed point: fin stabilization only works in atmosphere. A more practical Gauss weapon would use finned, slow spin projectiles in atmosphere, but different projectiles in vacuum. A good vacuum design would be an outer ring of dense material to carry angular momentum for spin stabilization, a slender core of dense armor piercing penetrator, with a ring of soft iron in between to stick the spin ring and poker together.

BigDogsRunning wrote: ↑
Depleted Uranium isn't ferromagnetic, so you couldn't launch a round "made" of DU with a Gauss weapon, but you could use DU as the core with a soft outer casing.
...
I'm guessing that most local governments, even if low law level, would be pretty frowny on people using DU rounds, as likely would the Imperium.

So use tungsten.

BigDogsRunning wrote: ↑
Also, If your round is pointed, has a teardrop tail, finned, and wasp-waisted, even though it is 4 mm, that won't be its diameter for its entire length, so you could easily justify a 4 g 4 x 40mm round, ...

The pointy bit will not add much length. Even at half tungsten and half steel it will be less than 30 mm long.

LBB4: Mercenary wrote:The round itself consists of a dense armor piercing core surrounded by a softer metal covering, ending in a hollow point, giving the round both high stopping power and a good armor piercing capability. Flight long the barrel is nearly frictionless with spin stabilization imparted through magnetic bias.

It's implied it's a slug, but a gauss bullet could be a fletchette to ensure stability.

It's basically the Vietnam era M193 ball bullet, as described in the original Mercenary.

Mercenary says:
"Gauss Rifle: The ultimate development of the slug thrower, the gauss rifle generates an electromagnetic field along the length of the barrel which accelerates a 4 mm, 4 gram needle bullet to velocities of 1500 meters per second. The round itself consists of a dense armor piercing core surrounded by a softer metal covering, ending in a hollow point, giving the round both high stopping power and a good armor piercing capability. Flight along the barrel is nearly frictionless, with spin stabilization imparted through magnetic bias."

Hasn't it been described as having a 10:1 aspect ratio? Didn't Marc Miller, or Loren write about a conversation on a plane with a ballistics guy from DARPA who said that there were designs for a wasp-waisted hypersonic flechette that was virtually silent? I have a vague recollection of reading that sometime in the last 40 years. Can anyone confirm, and source it, or am I imagining it?

My mistake, it's the 5.56 NATO SS109 that is 4 grams (62gr); as far as aspect ratio it wouldn't be 10:1 as described, it seems doubtful that it could have a 10:1 aspect ratio, as that would most likely rotate end to end. SS109's velocity is 945 m/s, 1/3rd less than what is described. I don't have any recollection of Marc writing about it, Frank wrote the original, so maybe he did, though I have never read anything by him about it.

Ye default shotgun fires off an eighteen millimetre shell; this might be a tad too large to stuff into a standard gauss rifle.

In an atmosphere, the gauss bullet does have to be aerodynamic, and have enough penetrative power to punch through personal armour, and deliver substantial energy to the target without passing through the body, completely.

As I understand physics, optimal subsonic speed is eighty five percent of mach, after which, it tends to get unstable.

It would look funny with a shotgun round stuck on the end of your Gauss Rifle.

If Gauss weapons are the ultimate expression of slug throwers, wouldn't they displace chemically propelled weapons of all calibres? What I was suggesting , was a new class of rail/coil guns that throw a larger calibre slug at lower speeds. If you launched a 20mm warhead, using a 21 x 210mm magnetic sabot, you could pack whatever kind of payload into a, say, 2cm x 4cm slug. It wouldn't have to be rapid fire, but it would be versatile.

That wouldn't be the only thing you could do. Just imagine, the Gauss weapon is the ultimate expression of projectile weapons. use it for different shapes of weapons.

[ . . . ]
Curious why gauss weapons do not have the zero-g trait. In all additions back to Classic the weapons are described as using electromagnetic effects to deliver the rounds. No chemical explosion hence no recoil... right?
[ . . . ]

Nope. The electromagnetic force accelerating the projectile still generates a corresponding force on the rifle - Newton's third law of motion still applies no matter what means is used to generate the force.

[ . . . ]
A problem with using DU rounds, is that the dust created by DU fragmenting and burning, creates a radioactive toxin that lingers in the environment for a while. I'm guessing that most local governments, even if low law level, would be pretty frowny on people using DU rounds, as likely would the Imperium.
[ . . . ]

This is a misconception with Depleted Uranium. U238 is only very slightly radioactive; the problem is not that it Depleted Uranium is a radioactive toxin in the way (say) Polonium-210 is, but that it's a heavy metal poison in much the same way that Mercury or Lead is. If you manage to ingest some it may have some radiological effects, but most of the toxicity is due to the chemistry of Uranium.

BigDogsRunning wrote: ↑
Depleted Uranium isn't ferromagnetic, so you couldn't launch a round "made" of DU with a Gauss weapon, but you could use DU as the core with a soft outer casing.
...
I'm guessing that most local governments, even if low law level, would be pretty frowny on people using DU rounds, as likely would the Imperium.

So use tungsten.

BigDogsRunning wrote: ↑
Also, If your round is pointed, has a teardrop tail, finned, and wasp-waisted, even though it is 4 mm, that won't be its diameter for its entire length, so you could easily justify a 4 g 4 x 40mm round, ...

The pointy bit will not add much length. Even at half tungsten and half steel it will be less than 30 mm long.

LBB4: Mercenary wrote:The round itself consists of a dense armor piercing core surrounded by a softer metal covering, ending in a hollow point, giving the round both high stopping power and a good armor piercing capability. Flight long the barrel is nearly frictionless with spin stabilization imparted through magnetic bias.

No fins necessary.

I'm guessing that Tungsten is the preferred penetrator material, much like now. Someone else brought up DU rounds.
The pointy bit isn't to add length, and the objective is to get a longer projectile, since that is more efficient for transferring magnetic force onto the round. You can have multiple layers of coils pulling/pushing different rings of ferromagnetic material in the shell of the round simultaneously. And the tungsten isn't just tacked onto the front like a warhead, it comprises the core of the round. making the round a long-rod penetrator, lots of mass, very little cross-section. this allows maximum penetrating power. You are correct that fins are not necessary, but if you have them, you can increase stability in an atmosphere, which increases long-range accuracy.

[ . . . ]
A problem with using DU rounds, is that the dust created by DU fragmenting and burning, creates a radioactive toxin that lingers in the environment for a while. I'm guessing that most local governments, even if low law level, would be pretty frowny on people using DU rounds, as likely would the Imperium.
[ . . . ]

This is a misconception with Depleted Uranium. U238 is only very slightly radioactive; the problem is not that it Depleted Uranium is a radioactive toxin in the way (say) Polonium-210 is, but that it's a heavy metal poison in much the same way that Mercury or Lead is. If you manage to ingest some it may have some radiological effects, but most of the toxicity is due to the chemistry of Uranium.

Excellent points Sir! You are absolutely correct, and I thank you for the clarification.
DU rounds have a tendency to leave a lot of dust around where they've been used, and you're right, heavy metal poisoning is the biggest long-term problem. Also, since it is "Depleted" Uranium, the radioactivity is reduced, however there is still some long-term effect. thank you for bringing this up. I hadn't researched as carefully as I usually do. I discovered that DU is roughly 40% less radioactive than Uranium, so not inconsequential, but not the main factor. The Heavy Metal poisoning will apparently destroy your kidneys well before the radioactivity will cause cancers. Yay!

Apparently the U.S. used 1-2000 metric tons of depleted uranium in Iraq, and the cleanup continues.